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Physics Seat P201 D. Baxter/R. Heinz EXAM #3 November 15, 2001 7:009:00 PM
INSTRUCTIONS 1. Sit in SEAT # given above. 2. DO NOT OPEN THE EXAM UNTIL YOU ARE TOLD TO DO SO. 3. Print your name (last name first) and blacken in the letters on the answer sheet with a #2 pencil. 4. Print your student number (identification number) and blacken in the numbers on the answer sheet with a #2 pencil. 5. Use the fronts and backs of the question sheets for scratch work. Do not use any other scratch sheets. 6. This is a multiple choice exam. Blacken in the answer to each question on the answer sheet. Fill in one and only one answer to each question. 7. Keep your eyes on your own work. 8. You have two hours to complete the exam. When you finish, please show your picture ID as you turn in your answer sheet. Please leave quietly so others are not disturbed. 9. THERE ARE 24 QUESTIONS. PLEASE ANSWER ALL OF THEM. THERE IS NO PENALTY FOR GUESSING!
You may use a calculator and three self-prepared sheets of formulas. You may also consult the appendices in the front and back of the book.
1.
A ventilation fan with a moment of inertia of 0.034 kg-m2 has a net torque of 0.11 N-m applied to it. What angular acceleration does it experience? a. b. c. d. e. 5.3 rad/sec2 4.0 rad/sec2 3.2 rad/sec2 1.9 rad/sec2 0.45 rad/sec2
2.
A merry-go-round has a moment of inertia of 500 kgm2 and a diameter of 4 meters. It rotates while empty at 1/3 revolution per second. When a parent of mass 125 kg jumps lightly on the rim (without causing any torque) the merry-goround changes speed. How many revolutions per second does it make after the parent jumps on? a. b. c. d. e. 5 4 2 1/3 1/6
3.
Consider two steel rods, A and B. B has three times the area and twice the length of A. The ratio of the Young's modulus for A divided by the Young's modulus for B will be: a. b. c. d. e. 5.0 3.0 2.0 1.0 0.5
4.
A uniform rod AB is 3 m long and weighs 4 N. It is suspended by strings AC and BD as shown. A block P weighing 24 N is attached at E, 3/4 m from A. The tension in the string BD is:
a. b. c. d. e.
8N 20 N 2N 6N 12 N
5.
A 240-N man stands halfway up a 13-m ladder of negligible weight. The base of the ladder is 5 m from the wall as shown. Assuming that the wall-ladder contact is frictionless, the wall pushes against the ladder with a force whose magnitude is:
12 m 5m a. b. c. d. e. 26 N 50 N 67 N 78 N 93 N
6.
A hoop, a uniform disk, and a uniform sphere, all with the same mass and outer radius, start with the same speed and roll without slipping up identical inclines. Rank the objects according to how high they go, least to greatest. a. b. c. d. e. disk, sphere, hoop disk, hoop, sphere sphere, hoop, disk sphere, disk, hoop hoop, sphere, disk
7. and 8.
Four equal point masses m are arranged in the x-y plane as shown. They are connected by light sticks to form a rigid body.
7.
The rotational inertia I about the y-axis of this array is: a. b. c. d. e. 2 ma2 4 ma2 6 ma2 8 ma2 10 ma2
a. b. c. d. e.
12 J 18 J 30 J 36 J 48 J
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8.
If I 8.0 kg m2 and the four masses shown in the figure above rotate about the y axis with an angular velocity of 3.0 rad/s, what is their total kinetic energy?
9.
A small disk of radius R1 is mounted coaxially with a larger disk of radius R2. The disks are securely fastened to each other and the combination is free to rotate on a fixed axle that is perpendicular to a horizontal frictionless table top. The rotational inertia of the combination is I. A string is wrapped around the larger disk and attached to a block of mass m, on the table. Another string is wrapped around the smaller disk and is pulled with a force F as shown. The acceleration of the block has a magnitude given by:
a. b. c. d. e.
R1F/mR2 R1R2F/(I - mR22 ) R1R2F/(I + mR22 ) R1R2F/(I - mR1R 2) R1R2F/(I + mR1R 2)
10.
A figure skater with arms initially extended starts spinning on the ice at 3 rad/s. She then pulls her arms in close to her body. Which of the following results? a. b. c. d. e. A smaller angular momentum A constant moment of inertia A greater angular momentum A smaller rotational rate A greater rotational rate
11.
A large tank holds a liquid uniform of density. The hydrostatic pressure at a given depth in the liquid depends upon: a. b. c. d. e. The total mass of the liquid. The surface area of the tank. The liquid's density. The shape of the tank. The volume of the tank.
a. b. c. d. e.
1955 kWh 1770 kWh 852 kWh 330 kWh 216 kWh
13.
How large a force is necessary to stretch a 2.0 mm-diameter steel wire ( Y 2.0 1011 N/m2) by 1.0%?
a. b. c. d. e.
3100 N 6300 N 9400 N 12500 N 2.0 109 N
14.
In simple harmonic motion about an equilibrium position, the restoring force must be proportional to the: a. b. c. d. e. amplitude frequency velocity displacement from the equilibrium position the square of the displacement from the equilibrium position
15.
A block of wood has density 0.50 gm/cm3 and mass 1500 gm. It floats in a container of oil. (The oil's density is 0.75 gm/cm3.) What volume of oil does the wood displace? a. b. c. d. e. 2900 cm3 2000 cm3 1500 cm3 1200 cm3 800 cm3
12.
A swimming pool heater has to be able to raise the temperature of the 4.00 104 gallons of water in the pool by 10.0 C. How many kiloWatthours (kWh) of energy are required? (One gallon of water has a mass of approximately 3.80 kg and the specific heat of water is 4186 J/kg-C (1 kWh = 3.60 MJ).)
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a. b. c. d. e.
0.1 T 0.75 T T 1.4 T 2.0 T
a. b. c. d. e.
1,960 N/m2 3,920 N/m2 7,840 N/m2 10,200 N/m2 15,700 N/m2
18.
Find the final equilibrium temperature when 10.0 grams of milk at 10.0C is added to 160.0 grams of coffee at 90.0C. (Assume the specific heats of the coffee and milk are the same as water and neglect the heat capacity of the container as well as any heat exchange between the container and the outside world.) a. b. c. d. e. 85.3C 77.7C 71.4C 66.7C 50.0C
19.
A brass plate is in the shape of a perfect square whose edge measures 12.395 cm when the plate is held at a temperature of 20.0C. What will be the area of this plate if it is cooled to -30.0C? ( brass 19 10 6 /C)
a. b. c. d. e. 153.99 cm2 153.74 cm2 153.52 cm2 153.34 cm2 152.84 cm2
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17.
A Boeing 737 airliner has a mass of 2.00 104 kg. The total area of the wings is 100.0 m2. What must be the pressure difference between the top and bottom of the wings to keep the airplane up?
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16.
A particle is in simple harmonic motion with period T. At time t 0 it is at the equilibrium point. At which of the following times is it farthest from the equilibrium point?
20.
A small hole of diameter 1 cm is poked through the metal side of a large cylindrical tank of diameter 10 m that contains water. The hole is 18 cm below the water surface. What is the initial velocity of outflow? (The density of water is 1000 kg/m3 and that of air is 1.29 kg/m3.) a. b. c. d. e. 1.9 m/s 2.5 m/s 3.2 m/s 3.5 m/s 4.1 m/s
21.
Estimate the volume of a helium-filled balloon at STP if it is to lift a payload of 5.00 102 kg. The density of air is 1.29 kg/m3 and helium has a density of 0.178 kg/m3. (The mass of the balloon and the helium inside the balloon are included in the payload.)
a. b. c. d. e.
4410 m3 1800 m3 932 m3 388 m3 225 m3
22.
In constructing a piece of scientific equipment an aluminum band of thickness 0.40 mm, width 1 cm, and inner diameter 0.9975 cm (at 25C) is heated to 400C so that it may be slipped over a brass cylinder of diameter 1.0000 cm (also at 25C). After the band cools back to 25C what will be the tension in the band? (Neglect any change in the diameter of the brass rod.) Al 24 10 6 /C, 19 10 6 , and YAl 7.0 1010 Pa. brass
a. b. c. d. e. 300 N 400 N 500 N 600 N 700 N
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23.
A silver bar of length 30 cm and cross-sectional area 1 cm2 is used to transfer heat from a 100C reservoir to a 0C block of ice. How much ice is melted per second? (For silver, k 427 W/m-C. For ice Lf 334, 000 J/kg.)
a. b. c. d. e.
5.6 grams/s 2.1 grams/s 0.82 grams/s 0.15 grams/s 0.043 grams/s
24.
Three identical horizontal uniform rods are each acted on by two or more forces, all perpendicular to the rods. Which of the rods could be in static equilibrium if the magnitudes of the forces were suitably adjusted (but not made zero)?
a. b. c. d. e.
Only 1 Only 2 Only 3 Only 1 and 2 All three
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